Cellulose based raw materials show immense potential as a foundational building block in the future bioeconomy. However, many novel methods remain in an embryonic state due to the lack of compatible process models and machinery. The research presented here explored novel processing routes and manufacturing methods for native cellulosic raw materials. The aim of this research was to investigate process domain bottlenecks by developing and testing prototype process machinery. The focus was on two manufacturing technologies, spinning and additive manufacturing.
Two different wet spinning methods were researched and laboratory scale spinning line prototypes were constructed for both spinning methods. The first spinning approach was based on a gel-like spinnable dope produced by dispersing pulp fibers with a deep eutectic solvent (DES). The dope was spun into fiber yarn using an inclined channel where the incipient yarn is stretched and transported with a stream of ethanol. The second spinning method was based on coaxial extrusion of a cellulose nanofibril (CNF) core and a supporting biopolymer shell around it. By using a shell of a rapidly coagulating biopolymer as support during filament formation, spinning rates and draw ratios were increased. The parameters associated with each process were studied experimentally and samples were characterized to evaluate the influence of process parameters. Improvements in throughput and properties of ensuing structures were demonstrated.
Additive manufacturing using high consistency enzymatically fibrillated cellulose nanofibrils (EFCNF) pastes was demonstrated. EFCNF is printable using a simple extrusion based method but the printed constructs undergo substantial deformation when air-dried. A 3D scanning based drying deformation quantification was developed to determine the extent of the deformation as well as the influence of process conditions on it. Results indicated that despite a substantial decrease in volume and change in aspect ratio the original design intent is preserved.
An open-source extruder design was developed for improving dosing accuracy as well as improving monitorability of the extrudate rheology during printing. The mechanical components of the extruder can be manufactured using entry-level 3D printing equipment and the price of the required components is less than a tenth of commercially available equivalent extruders.
In summary, this work demonstrates how process domain requirements can be taken into account in concurrent machine design and material development. The research highlights how concurrent multidisciplinary development is advantageous as knowledge regarding requirements propagates more efficiently across the different domains resulting in more informed design decisions.
|Publication status||Published - 2019|
|MoE publication type||G5 Doctoral dissertation (article)|
- cellulose, bioproduct, spinning, additive manufacturing, 3D printing